As an index to evaluate runability of a magnetic tape, a measurement of friction force between a magnetic head and magnetic tape is widely performed and as a measuring method of running fiction of the magnetic tape, until now a following method has been adopted. In the method, firstly the magnetic tape is wound around a guide post of which material is same as that of a magnetic head, a weight is attached to one end of the magnetic tape, and on the other hand, a strain gauge is connected with the other end. Then, the strain gauge is pulled at a predetermined abrasion speed, tension at that time is measured by the strain gauge, and the friction force is calculated based on the tension.
However, although the conventional measurement method can calculate the friction force between the magnetic tape and guide post used instead of the magnetic head, it cannot accurately grasp the friction force between the magnetic head and magnetic tape practically running within a magnetic drive. In this connection, to handle this problem, there conventionally exists a measurement device to measure the friction force between the magnetic head and magnetic tape practically running within the magnetic drive by detecting a torque burdening a rotation shaft of a rotation head (for example, see FIG. 3 in Japan patent laid open publication 05-187993). However, the measurement device cannot be utilized for measuring the friction force within the magnetic tape drive with an unrotating head.